Mounts for electron tubes having filamentary cathodes



May 10, 1955 2,708,248

N. H. GREEN MOUNTS FOR ELECTRON TUBES HAVING FILAMENTARY CATHODES FiledApril 28, 1951 INVENTOR Nurval Hflre E11 United States Patent MOUNTS FORELECTRON TUBES HAVING FILAIWENTARY CATH'JDES Norval H. Green, HasbrouckHeights, N. 1., nssignor to Radio Corporation of America, a corporationof Betaware Application April 28, 1%1, Serim No. 223,484

6 Claims. (Cl. 313-261) The present invention relates to mounts forelectron tubes, and more particularly to a mount having elements forfacilitating the assembly of a filamentary cathode therein.

, Electron tube mounts having a filamentary cathode are usuallyassembled with elements of the mount, such as spacer plates and otherelectrodes, in concentric relation around the cathode. The assembly ofthe cathode in the mount is usually accomplished after the otherelectrodes have been assembled and requires a threading hereof throughapertures in the spacer plates and through a central passagewayextending through the other electrodes. The insertion or threading ofthe filamentary cathode is a relatively slow and tedious operation because the filament or Wire of the cathode is flexible and thereforecannot be pushed through the apertures on the spacer plates and thepassageway through the other electrodes. Where a tab is fixed to eachend of the filamentary cathode to facilitate welding the ends of thefilament to heavier lead-in connections, the threading operation isrendered increasingly difiicult, because the tab is likely to catchonelements of the mount, such as the grid wire of a wound type grid. Wheresmall size tubes are involved, the apertures in the spacer plates forreceiving the filament are relatively small and the space defined by theelectrode adjacent the filament is relatively narrow. This furtherincreases the difiiculty of threading the filamentary cathode intoappropriate position in the mount.

Accordingly it is an object of the invention to provide an improvedmount wherein the assembly of a filamentary cathode in the mount isfacilitated.

- A further object is to provide a mount for a relatively small sizedtube, including a filamentary cathode, wherein the cathode is supportedon exposed supports for ease in mounting.

Another object is to provide an electron tube mount having a structurefor rendering the assembly-of a filamentary cathode therein equallyexpeditious inmounts of different size including mounts for miniatureand subminiature tube types.

A further object is to'provide a mount wherein a filamentary cathode isextendable laterally into desire position in the mount.

'Another object is to provide a mount of generally tubular outline andhaving a peripheral indentation for receiving a filamentary cathode in arelatively simple operation.

A further object is to provide a mount including two axially spacedparallel spacer plates having peripheral indentations therein forfacilitating receipt and proper orientation of a filamentary cathode inthe mount.

- Another object is to provide an electron tubemount having afilamentary cathode,. and other electrodes of modified form to permitmounting the cathode from a. side of the mount to facilitate assembly ofthe cathode in the mount.

Briefly considered, the electron tube mount of the invention includestwo spaced parallel spacer plates having registering slots extendinginwardly from the peripheries thereof. The bottoms of the slots areadapted to engage and position a filamentary cathode. Other electrodes,such as a grid and anode, are mounted between the spacer plates inaccurate registry with the bottoms of the slots referred to. The otherelectrodes referred to are so constructed that no portion thereofextends across the slot. The slot therefore provides a free passagewayfor extension of the cathode laterally of the mount into engagement withthe slot bottoms for accurate registry with the other electrodes of themount.

The lateral assembly of the cathode in the mount avoids the dificultiesabove referred to that characterize the axial extension of the cathodein the mount required by prior mount constructions. The mount of theinvention is particularly advantageous in connection with small sizedelectron tube mounts. While the present trend is towards relativelysmall size electron tubes using filamentary cathodes, reduction in sizehas been accompanied heretofore by the very serious limitations imposedby the increased difiiculty of inserting the cathode in the mount. Theinvention therefore removes one serious obstacle to further progress inthe direction of reduced size of electron tubes.

Further objects and advantages of the invention will be made clear asthe description continues.

For a better understanding of the invention a description of twoembodiments thereof will be presented by way of example, taken inconnection with the appended drawing in which:

Figure 1 is an elevation partly in section of an electron tube includingthe invention;

Figure 2 is an elevation of a grid structure employed in the tube shownin Figure 1;

Figure 3 is a persepctive view of the anode used in the tube of Figure1;

Figure 4 is a transverse sectional View along the line 4-4 of Figure land shows a top view of the mount of the tube depicted in Figure 1;

Figure 5 is a transverse sectional view along the line 55 of Figure land shows the electrode arrangement of the tube; and

Figure 6 is a top view of a mount embodying a modification of theinvention.

Referring now in more detail to the drawing, an electron tube in whichthe invention is included is shown in Figures 1 to 5. This electron tubeincludes an envelope 10, to one end of which is afiixed a base 11 havingcontact prongs 12 suitably connected to electrodes of an electrode cagewithin the envelope.

The electrode cage includes two spaced insulating spacer plates 13, 14which may be of mica, for example. Between the spacer plates referred toare mounted electrodes comprising agrid 15, an anode having sections 16,16a and two filamentary cathodes 17, 18. The anodev sections may beconnected to each other electrically.

The grid 15, as shown in Figures 2 and 5, includes two plates 19, 20having slots 21, 22 and side wings 23, 24;

The two plates 19, 20 are fixed as by welds 25, to a sup-' port plate26, having cars 27, 28, shown in Figure 4, for fixing the grid at eachend thereof to the spacer plates 13, 14. The plates 19, 29 are sooriented on the supportplate 26, that adjacent slots 21, 22 on the twoplates are in registry as shown in Figure 5. The side wings 23, 24' areprovided for facilitating the assembly of the filamentary cathode in theamount, aswill appear more fully v in the following. j 1

The anode comprises two similar sections 16, 16a, one of which is shownin Figure 3. Each section includes spaced plates 31, 31a, having edges29, 30. The spaced plates are tied together by integral strips 32, 32a.Each anode section: is provided with ears 33 at its upper and lower endsfor engaging the spacer plates 13, 14, the

'upper ears being shown in engagement with the upper are in registrywith the slots 21, 22 in: the grid plates Each of the spacer plates 13,14 is provided with peripheral indentations or slots 34, 35 shown inFigures 4 and S. The slots in each of the plates have bottom edges 36,37 disposed in predetermined accurate registry with the space betweenthe registering slots 21 and the registering slots 22. Thus whenfilamentary cathodes are extended laterally through the slots 34, 35 inthe spacer plates 13, 14 and into engagement with the bottom edges 36,37, each of the cathodes will be in accurate registry with tworegistering slots in the grid plates 19, 20 and with one of the edges29, 30 on each of the two anode sections 16, 17. The filamentarycathodes may be supported at their upper ends by tension hooks 38, 3?fixed to standards 40, 41 extending through the'mount and fixed to thespacerplates 13, 14.

It will be noted from the foregoing that the mount described isparticularly advantageous as regards extension of the filamentarycathodes therein. The mount permits the filaments to be assembled in themount by extending'them laterally into the slots 34, 35 in the twospacer plates of the mount. During the extending operation no forceisapplied to a filament axially thereof so that there is no danger ofbuckling of the filament. In

'fact, the filament may be supported at both ends thereof during amounting operation to provide further assurance against deformation.Furthermore, the path for the filament during an inserting operationprovided by the slots in the spacer plates is free from interference byother electrodes or mount parts, so that there is complete freedom fromcontact between the filament and such parts during a filament insertingoperation. To particularly assure freedom from cathode contact with thegrid plates 19, 20, the grid plate wings 23, 24 are bent outwardly toprovide a separation at their free edges that exceeds that of oppositewalls of the slots 34, 35.

But utilizing the edges 29, 30 of the anode sections as theactive'surfaces of the anode, very close spacings are permitted betweenthe anode and grid. Moreover, this spacing is maintained uniform duringoperation of the tube due to the freedom from buckling of the activesurfaces of the anod'e'in the direction of the grid. Where a flat andrelatively large surface of the anode faces the grid, any bucklingthereof that might occur in response to'temperature conditions within adevice in which it is the invention to a side insertion of a filament,such as is accomplished by rendering the edges 29, 30 of the anode theactive surfaces thereof, the further advantages of such anode structure,as referred to above, are realized.

Moreover, the grid in the embodiment shown is of filamentary cathode 54in an electrode assembly. To

this end, two spaced insulating spacer plates, one of which is shown at42, are provided with indentations or slots 43 extending from a centralportion of the plates to their peripheries. Adjacent the peripheries ofthe plates, the slots are flared as shown at 44 to facilitate a sideextension of the filament. thereinto.

To avoid contact with other electrodes of the mount during the operationof extending the filament therein, the grids, which. may be. three innumber, 45, 46, 4.7,. are supported to one side of the plane of gridside rods 48 and bent away from the plane of the side rods to clear thebottom 49 of the slot 43. The anode may include two spaced plates 50, 51connected together by a strap 52 disposed out of registry with the slot43. The anode plates are fixed to the spacer plates by means of ears 53bent against the plates.

The bottom 49 of the slot 43 may be disposed beyond the plane of theside rods 48, as shown in Figure 6, to dispose the filament relativelyclose to the'number one grid 47. Instead of disposing the slot 43 asshown, the grids may be flattened to a greater degree than shown tosecure the desired spacing between the filamentary cathode 54 and thegrids. The cathode 54 is supported resiliently by a filament anchor wire55 which is in turn fixed to a standard 56 suitably supported in themount.

It will be apparent from the foregoing that I. have provided an improvedmount having a filamentary cathode and that is characterized byincreased facility in the assembly of the cathode therein. The mount isparticularly suited for relatively small sized electron tubes and fortubes of indifferent size having criticalcharacteristic requirements.

What is claimed is: I

1. An electron tube mount comprising an insulating spacer plate, havingslots at opposite edge portions thereof communicating with the peripheryof said plate,

a grid structure comprising two electrodessupported'onsaid plate andhavingactive portions adjacent the side edges and closed ends only. ofsaid' slots, and filamentary cathodes extending through said slotsaxially of said tube and adjacent said active portions, whereby saidcathodes are adapted to be positioned in predetermined orientation withrespect to said grid in a relatively easy side extension thereof intosaid slots.

2. An electron tube mount comprising an insulating spacer plate having aslot extending inwardly from the periphery thereof, an anode supportedon said plate and having opposite edges in registry across said slot, 9.grid supported on said plate and havingactive portions in registry withsaid edges, said grid having a flared open side adjacent the peripheryof said plate, and a fiIa-' mentary cathode supported in said slot inregistry with said opposite edges and said active portions, whereby a Iin assembly is provided.

3. An electron tube mount comprising an anode,-said anode comprising aU-shaped' structure including two spaced parallel plates in'faceregistry connected by a mount having increased ruggedness and increasedfacility transverse portion at adjacent longitudinal edges thereof,

the edges of said plates opposite said adjacent edges defining the soleactive anode portion of said structure, said structure being mountedwith said active anode portions extending longitudinally of the mount, agridcomprising a plate having slots in registry with said active anodeportions and filamentary cathodes in registry with said active anodeportions and said slots, whereby a ruggedized mount is provided.

4. A mount for an-electron tube comprising a grid including three platesin sandwiched relation, having two of .said plates exposed, said twoexposed plates being wider than the intermediate one of said plates,said two plates including spaced portions extending beyond oppo-. site'sides of said intermediate plate, said portions on each of said sidesdefining an 'open sided rectilinear said channels, said opposite sidesof said intermediate plate being spaced farther from the peripheryof'said plate than the bottoms of said indentation therein, an anode.having edge portions only disposed in. opposite relation across saidopposite slots and extending along said channel, and cathode filamentsbearing against said bottoms of the indentations and extending alongsaid channel in lateral registry with said opposite slots and edgeportions, whereby a ruggedized and easily assembled mount is provided.

5. A mount for an electron tube comprising an elongated fiat gridstructure having two wings extending from opposite sides thereof, saidgrid structure having longitudinal slots therein, said Wings definingtroughs having bottoms extending along said opposite sides or" the gridstructure, insulating spacer plates supporting said grid structure, saidplates having peripheral indentations partly registering with saidtroughs, said indentations having bottom bearing portions closer to theperiphery of said plates than the bottoms of said troughs, and cathodefilaments engaged by said bearing portions spacing said filaments fromsaid grid wings, said bottom bearing portions disposing said filamentsin lateral registry with said longitudinal slots.

6. An electron tube mount comprising two spaced 20 insulating plates,said plates having indentations at opposite edges thereof, an anodesupported between said plates and comprising two U-shaped portionshaving edges only in registry across said indentations and definingslots, said indentations having bottoms lying in the spaces betweenopposite ones of said edges, two filamentary cathodes supported in saidslots, and spring means mounted on one of said plates and in a planeextending between said indentations thereof for urging said cathodesagainst said bottoms, whereby a mount structure is provided adapted toprovide a relatively easy assembly of said cathode therein.

References Cited in the file of this patent UNITED STATES PATENTS2,115,934 Smith May 3, 1938 2,250,409 Krahl July 22, 1941 2,433,410Walker et al Dec. 30, 1947

